1. Field of the Invention
The present invention relates generally to a multi-hop relay cellular network, and in particular, to a frame configuration method and apparatus for supporting multiple links in a multi-hop relay cellular network using two frequency bands.
2. Description of the Related Art
Today, many people carry lots of digital electronic devices such as laptop computers, handheld phones, Personal Digital Assistants (PDAs), Moving Picture Experts Group (MPEG) Audio Layer 3s (MP3s), etc. Most of them run independently without interworking. If the portable digital electronic devices may form a wireless network without the aid of a central control system, the individual devices can share a variety of pieces of information easily with one another and thus can provide unprecedented and diverse information services. Such a wireless network enabling communications among the devices without the aid of the central control system irrespective of time and place is called an ad hoc network or a ubiquitous network.
One critical requirement for deployment of a 4th Generation (4G) mobile communication system under recent active research is to build a self-configurable wireless network.
A self-configurable wireless network is a wireless network that is configured in an autonomous or distributed manner without control of a central system to provide mobile communication services. A 4G mobile communication system installs cells of very small radiuses for the purpose of enabling high-speed communications and accommodating a larger number of calls. A conventional centralized wireless network design is not feasible for a self-configurable wireless network. Rather, such a wireless network should be built to be under distributed control and to actively cope with an environmental change like an addition of a new Base Station (BS). That's why a 4G mobile communication system uses a self-configurable wireless network configuration.
For real deployment of a self-configurable wireless network, techniques used for an ad hoc network should be introduced to a mobile communication system. A major example of them is a multi-hop relay cellular network built by applying a multi-hop relay scheme used for the ad hoc network to a cellular network with fixed BSs.
In general, since a BS and a Mobile Station (MS) communicate with each other via a direct link in the cellular network, a highly reliable radio link can be established easily between them.
However, due to the fixedness of the BSs, the configuration of the wireless network is not flexible, making it difficult to provide an efficient service in a radio environment experiencing a fluctuating traffic distribution and a great change in the number of calls.
These drawbacks can be overcome by a relay scheme of delivering data over multiple hops using a plurality of neighbor MSs or neighbor Relay Stations (RSs). A multi-hop relay scheme facilitates fast network reconfiguration adaptive to an environmental change and renders an overall wireless network operation efficient. Also, a radio channel in a better channel status can be provided to an MS by installing an RS between the BS and the MS and thus establishing a multi-hop relay path via the RS. What is better, since high-speed data channels can be provided to MSs in a shadowing area or an area where communications with the BS is unavailable, cell coverage is expanded.
FIG. 1 shows a typical multi-hop relay cellular network. An MS 110 within the service area 101 of a BS 100 is connected to the BS 100 via a direct link. On the other hand, an MS 120, which is located outside the service area 101 of the BS 100 and thus in a poor channel state, communicates with the BS 100 via a relay link of an RS 130.
The RS 130 provides better-quality radio channels to the MSs 110 and 120 when they communicate with the BS 100 but in a bad channel state as they are located at a boundary of the service area 101. Thus, the BS 100 can provide a high-speed data channel to the cell boundary area using a multi-hop relay scheme and thus expand its cell coverage. As shown in FIG. 1, there are a BS-RS link and an RS-MS link as well as a BS-MS link when a relay service is used in the cellular network.
To enable the MS to communicate with the RS as well as with the BS under circumstances in the multi-hop relay network, resources of the air interface must be dynamically distributed between the BS and the RS.
One or more frequency bands can be allocated to a service provider in the cellular network. Therefore, there exists a need for a communication mechanism for efficiently using the radio interface resources on multiple links using one or more frequency bands in the multi-hop relay cellular network.